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  • Author or Editor: M.A. Meli x
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Abstract  

The knowledge of radioactive and stable elements partitioning to natural sediment systems is essential for modelling their environmental fate. A sequential extraction method consisting of six operationally-defined fractions has been developed for determining the geochemical partitioning of natural (U, Th, 40K) and antropogenic (Pu, 241Am, 137Cs) radionuclides in a 10 cm deep sediment sample collected in the Tyrrhenian sea (Gaeta Gulf, Italy) in front of the Garigliano Nuclear Power Plant. 137Cs and 40K were measured by gamma-spectrometry. Extraction chromatography with Microthene-TOPO (U, Th), Microthene-TNOA (Pu) and Microthene-HDEHP (Am) was used for the chemical separation of the alpha-emitters: after electrodeposition alpha-spectrometry was carried out. Some stable elements (Fe, Mn, Al, Ca, Pb, Ba, Ti, Sr, Cu, Ni) were also determined in the different fractions to get more information about the chemical association of the radionuclides.

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Summary  

Naturally occuring radioactive materials (NORM) are present in the environment and can be concentrated by technical activities, particularly those involving natural resources. These NORM deposits are highly stable and very insoluble under environmental conditions at the earth's surface. However, reducing or oxidant conditions or pH changes may enable a fraction of naturally occurring radionuclides to eventually be released to the environment. In this paper the leachability of210Pb and210Po was determined in three samples coming from a refractories production plant (dust, sludge, finished product), in one dust sample from a steelwork and in one ash sample coming from an electric power station. A sequential extraction method consisting of five operationally-defined fractions was used. The average leaching potential observed in the samples from the refractory industry is very low (mean values: 5.8% for210Pb and 1.7% for210Po). The210Pb and210Po leachability increases for the ash sample coming from an electric power plant using carbon (17.8% for210Pb and 10.0% for210Po); for the dust sample coming from a steelwork, the percent soluble fraction is 41.1% for210Pb and 8.5% for210Po. For all samples the results obtained show that210Pb is slightly more soluble than210Po.

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Abstract  

Low specific activity scales consisting of alkaline earth metal carbonates and sulfates are often present in some gaseous and liquid hydrocarbon plants; these scales contain a certain concentration of radium, uranium and thorium, which can cause a risk of -irradiation and of internal radiocontamination when they must be mechanically removed. That being stated,238U,232Th and226Ra were determined in scales, sludges and waters coming from different plants.238U and232Th concentrations were found very low; the isotopes238U and234U resulted in radioactive equilibrium, whilst232Th and228Th were not always in equilibrium.226Ra concentration was higher in scales and sludges than in waters.

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